The wind energy industry announced a plan today aimed at reducing by a third the number of bats killed by turbines.

The plan, developed by the American Wind Energy Association and backed strongly by bat advocates, would reduce the speed of turbines during bats’ fall migration, preventing up to 100,000 bat deaths annually with only minor losses in electricity generation.

The new operating protocol has been adopted by 17 of AWEA’s member companies that last year owned about 60 percent of the nation’s installed wind capacity.

“This is a landmark practice,” said John Anderson, AWEA’s senior director of permitting policy and environmental affairs. “We’re doing this because it’s the right thing to do.”

The strategy was shaped by a decade of research by the Bats and Wind Energy Cooperative, which includes AWEA, Bat Conservation International, the Fish and Wildlife Service, the National Renewable Energy Laboratory, the Energy Department, the U.S. Geological Survey and the Association of Fish and Wildlife Agencies. The cooperative was formed in 2003 after industry discovered a higher-than-anticipated number of dead bats at turbine farms in Pennsylvania and West Virginia, said Cris Hein, director of the bats and wind energy program at BCI.

Until then, much of the concern around wind farms surrounded birds, particularly raptors, but “nobody had any idea that bats would be an issue,” Hein said.

Today, scientists believe hundreds of thousands of bats are killed annually by wind turbines, culling from the landscape a key insect eater and ally to area farmers.

Under today’s agreement, participating companies will reprogram their turbines to slow down in low-wind conditions during bats’ migration season, typically mid-August to late October. When temperatures are above 50 degrees Fahrenheit and winds are below “cut-in” speeds – the speed at which significant electricity is generated, or 7 to 8 mph – turbine blades will be “feathered,” meaning they will be turned parallel to the direction of the wind.

Blades will only revolve one to three times a minute – slowly enough to greatly curtail bat collisions.

Anderson said the new operating protocols will collectively cost participating companies “millions” of dollars in lost electricity generation and the reprogramming of turbines, in addition to some wear and tear to the facilities.

While birds are protected under the Migratory Bird Treaty Act and the Bald and Golden Eagle Protection Act, there is no federal law protecting bats that aren’t threatened or endangered.

Migratory, tree-roosting bats – including the eastern red bat, the silver-haired bat and the hoary bat – stand to gain the most from today’s agreement, Hein said. Those three species represent 78 percent of bat deaths from wind farms, according to BCI.

Most bat fatalities occur during the three-month migration from Canada to the southern United States and Mexico.

There’s evidence to suggest that bats are actually attracted to these turbines, Hein said. They roost in trees and may mistake the towers as a place to roost, to find other bats or find insects, Hein said.

The feathering technique during migration season is expected to avoid roughly a third of bat deaths, a number calculated by scientists commissioned by BCI based on data from operating wind farms in the East and Midwest, Anderson said.

That technique could spare a large number of bats.

Consider a 2013 study by Ed Arnett of the Theodore Roosevelt Conservation Partnership and Erin Baerwald of the University of Calgary that estimated between 840,486 and 1.7 million bats died at wind farms in the dozen years leading up to 2011. In 2012, up to 396,000 bats could have been killed, the scientists concluded.

“It’s a lot of bats, and kills should be mitigated,” Arnett said. “The only proven approach is by what is called ‘raising turbine cut-in speed.’”

In 2010, Arnett authored a study that tested the effectiveness of raising the cut-in speed at the Casselman Wind Power Project in Somerset County, Pa., over a two-year period.

The study found that “relatively small changes” to wind turbine operation reduced nightly bat mortality by between 44 and 93 percent, while total annual electricity output was reduced by less than 1 percent, the study found.

The cost to implement the new AWEA protocol won’t be insignificant to participating companies, Anderson said. Yet the curbs on turbine speeds will come when there wouldn’t be a lot of energy generation anyway.

He said he anticipates more companies coming on board.

“This measure has been formally adopted by AWEA, and the hope and expectation would be that all developers and owner/operators would employ it when risks to bats warrant its use,” Anderson said. “We’re really hopeful this demonstrates the wind industry holds itself to a higher standard.”

Group tests new technology

BCI said the new strategy comes at a critical time, as wind energy in the United States is expected to expand by sixfold by 2030, with potentially “devastating” impacts on bat populations.

To further mitigate the threat, BCI is also exploring a technology known as ultrasonic acoustic deterrents, which was found to reduce bat fatalities at one wind farm in 2009 and 2010 by as much as 64 percent.

Hein said the technology is not quite ready for prime time, but that the theory of deterring bats is sound. BCI in April received part of $1.75 million from the Energy Department to develop technologies that will reduce the impacts of wind facilities on bats.

The DOE money will allow BCI researchers to conduct reliability tests for the electronic deterrent device and carry out a full-scale validation of its effectiveness at a wind energy facility.

Both strategies are key for bats, which serve a critical ecological role by eating insects and saving the agricultural sector billions of dollars in pesticide use, Hein said.

“They keep our produce, our crops cheaper,” he said. “They provide an ecological service in keeping these things in check.”

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